1. Field of the Invention
The invention relates to a process for use with a companion electronic article surveillance (EAS) system. The inventive process detects and magnetizes a magnetic security marker of the EAS system.
The invention relates further to apparatus for practicing the aforesaid process.
2. Prior Art
U.S. Pat. No. 3,820,104 discloses a process of the aforesaid kind whereby a magnetic security marker particularly for anti-pilferage systems may be detected within a detection zone and deactivated thereafter, with the fact of such deactivation having taken place being signalled. The prior art process deactivates the magnetic security marker by magnetizing an element therein. The magnetizing field is preferably produced by discharging a capacitor having a very high capacitance into a coil. The process requires a very high voltage since it would not be possible otherwise to furnish the required current for two successive deactivation pulses at an acceptable repetition rate. This also calls for a voluminous and relatively expensive capacitor discharge circuit to be incorporated in the apparatus for practicing the said process.
It has been known also to provide apparatus for detecting and deactivating a security strip attached to an article of merchandise (DE-OS 30 45 703) which comprises a chamber having at least an input and an output opening for receiving the articles, as well as interrogation, detection and deactivation coils surrounding said chamber which when coupled to the associated power source are energized to generate an electromagnetic field which permeates the said chamber.
DE-OS 30 14 667, too, discloses a process and apparatus for deactivating a security marker much like that described in the U.S. Pat. No. 3,820,104.
In both of the disclosures, the security marker comprises a strip of magnetically soft (low coercive force) high-permeability material together with at least one piece of a second material having a higher coercive force which in the demagnetized condition is neutral relative to and does not affect the magnetically soft strip so that in this condition the security marker will be activated, meaning that the detection means will detect a characteristic response produced by the marker when an article having the marker attached thereto passes through the surveillance zone.
In order to deactivate the security marker (e.g. when the merchandise has been paid for), the deactivator magnetizes the higher coercive force material and causes the high-permeability element to saturate so that the characteristic response on which detection is based is no longer produced.
When using a deactivator in the form of a coil, the associated field magnetizes a continuous strip of the magnetizable material into a single one-piece bar magnet since the magnetic field lines will be short-circuited in the latter and be prevented from extending sufficiently through the material of a high-permeability material. As a result, there is not acceptable safety that the high-permeability strip be saturated to the point where it cannot respond to an alternating magnetic field in the surveillance zone. In order to prevent this from happening, the process known by DE-OS 30 14 667 depicts apparatus for forming adjacent poles of different polarity in the magnetic security marker by moving the marker into the active region of a deactivator which has adjacent poles of different polarity. The deactivator and reactivator for the magnetizable security marker used there disclosed comprises alternating polarity magnetic poles serially spaced on a mount. The distance between said poles are selected to correspond to the desired depth of penetration of the magnetic field generated between adjacent poles, and each pole has a deactivation coil wound thereon, with adjacent coils being serially connected and wound in opposite directions so that a current passed therethrough causes webs in the mounting structure, which forms the poles, to act alternatingly as north poles and south poles.
The prior process and apparatus according to DE-OS 30 14 667 are unable to determine safely whether the security element has in fact been demagnetized or deactivated.